Plasma display device and control method thereof

Abstract

A plasma display device and display method are provided. The plasma display device expresses a video with gradations by controlling lighting of subfields forming one field, each of the subfields having a weighted luminance. A load factor calculation unit calculates a display load factor of an input video signal. A sustain pulse number change and control unit changes and controls a total number of sustain pulses of one field according to the display load factor. A gradation number conversion processing unit selects a gradation number expressed by the plasma display device according to the total number of sustain pulses and converts the input video signal into a display video signal of the selected gradation number. An error diffusion processing unit spatially diffuses a value corresponding to a decimal fraction when the gradation value of the display video signal in the selected gradation number has the value corresponding to the decimal fraction.

1 . A plasma display device expressing a video with gradations by controlling lighting of each of a plurality of subfields forming one field, each of the subfields having a weighted luminance, comprising:
 a load factor calculation unit calculating a display load factor of an input video signal;   a sustain pulse number change and control unit changing and controlling a total number of sustain pulses of one field according to the display load factor;   a gradation number conversion processing unit selecting a gradation number expressed by said plasma display device according to the total number of sustain pulses and converting the input video signal into a display video signal of the selected gradation number; and   an error diffusion processing unit spatially diffusing a value corresponding to a decimal fraction when the gradation value of the display video signal in the selected gradation number has the value corresponding to the decimal fraction.   
   
   
       2 . The plasma display device according to  claim 1 ,
 wherein said gradation number conversion processing unit selects the gradation number based on a ratio between a luminance weight of a lowest subfield having a smallest luminance weight among the plural subfields and a luminance weight corresponding to the total number of sustain pulses.   
   
   
       3 . The plasma display device according to  claim 1 ,
 wherein a luminance weight of a lowest subfield having a smallest luminance weight among the plural subfields is fixed even when the display gradation number is changed.   
   
   
       4 . The plasma display device according to  claim 2 , wherein the luminance weight of the lowest subfield is fixed even when the display gradation number is changed. 
   
   
       5 . The plasma display device according to  claim 3 ,
 wherein the number of plural subfields forming the one field is fixed even when the total number of sustain pulses is changed.   
   
   
       6 . The plasma display device according to  claim 4 ,
 wherein the number of plural subfields forming the one field is fixed even when the total number of sustain pulses is changed.   
   
   
       7 . A display method of a plasma display device expressing a video with gradations by controlling lighting of each of a plurality of subfields forming one field, each of the subfields having a weighted luminance, said method comprising:
 calculating a display load factor of an input video signal;   calculating a total number of sustain pulses of one field according to the display load factor;   selecting a gradation number expressed by said plasma display device according to the total number of sustain   pulses and converting the input video signal into a display video signal of the selected gradation number; and   spatially diffusing a value corresponding to a decimal fraction when the gradation value of the display video signal in the selected gradation number has the value corresponding to the decimal fraction.   
   
   
       8 . The display method of the plasma display device according to  claim 7 ,
 wherein the gradation number is selected based on a ratio between a luminance weight of a lowest subfield having a smallest luminance weight among the plural subfields and a luminance weight corresponding to the total number of sustain pulses.   
   
   
       9 . The display method of the plasma display device according to  claim 7 ,
 wherein a luminance weight of a lowest subfield having a smallest luminance weight among the plural subfields is fixed even when the display gradation number is changed.   
   
   
       10 . The display method of the plasma display device according to  claim 8 ,
 wherein the luminance weight of the lowest subfield is fixed even when the display gradation number is changed.   
   
   
       11 . The display method of the plasma display device according to  claim 9 ,
 wherein the number of plural subfields forming the one field is fixed even when the total number of sustain pulses is changed.   
   
   
       12 . The display method of the plasma display device according to  claim 10 ,
 wherein the number of plural subfields forming the one field is fixed even when the total number of sustain pulses is changed.   
   
   
       13 . A display method of a plasma display device displaying a video with gradations by controlling lighting of each of a plurality of subfields forming one field, each of the subfields having a weighted luminance, said method comprising:
 when changing a total number of sustain pulses in one field of sustain pulses for displaying the video with gradations,   selecting a gradation number expressed by said plasma display device according to the changed total number of sustain pulses and converting the input video signal into a display video signal of the selected gradation number; and   performing error diffusion on a decimal fraction part of a gradation value of the display video signal caused by the conversion.   
   
   
       14 . The display method of the plasma display device according to  claim 13 ,
 wherein the gradation number is selected based on a ratio between a luminance weight of a lowest subfield having a smallest luminance weight among the plural subfields and a luminance weight corresponding to the total number of sustain pulses.   
   
   
       15 . The display method of the plasma display device according to  claim 13 ,
 wherein a luminance weight of a lowest subfield having a smallest luminance weight among the plural subfields is fixed even when the display gradation number is changed.   
   
   
       16 . The display method of the plasma display device according to  claim 14 ,
 wherein the luminance weight of the lowest subfield is fixed even when the display gradation number is changed.   
   
   
       17 . The display method of the plasma display device according to  claim 15 ,
 wherein the number of plural subfields forming the one field is fixed even when the total number of sustain pulses is changed.   
   
   
       18 . The display method of the plasma display device according to  claim 16 ,
 wherein the number of plural subfields forming the one field is fixed even when the total number of sustain pulses is changed.